Small Animal Dermatology, 3rd edition

432 DISEASES/DISORDERS

Primary Keratinization Disorders

 Ichthyosis:
Present at or near birth
Nonepidermolytic and epidermolytic; nonepidermolytic most common and

associated with defects in various components of the epidermis; epidermolytic

caused by a defect in keratin synthesis

Nonepidermolytic ichthyosis: autosomal recessive mutations affecting lipids and

structural proteins; West Highland white terrier, golden retriever, doberman

pinscher, Irish setter, collie, American bulldog, American Staffordshire terrier,

Boston terrier, Labrador retriever, Jack Russell terrier, Manchester terrier, Aus-

tralian terrier, cairn terrier, Norfolk terrier, Yorkshire terrier, soft-coated wheaten

terrier (Figure 29.1)

Golden retriever ichthyosis (nonepidermolytic ichthyosis): mutation in the

PNPLA1 gene that plays a role in lipid metabolism and organization in the epi-

dermis; genetic testing available to assess for carrier status; characterized by large

soft white adherent scale prominent on the trunk; diagnosed by 1 year of age

(Figure 29.2)

American bulldog ichthyosis (nonepidermolytic ichthyosis): mutation in the

NIPAL-4 gene that leads to decreased expression of the protein icthyin which

is involved in epidermal lipid metabolism; genetic test available to assess car-

rier status; characterized by severe scruffy scaling haircoat, glabrous skin is

erythematous with adherent light brown scale giving a wrinkled appearance;

Malasseziadermatitis is a common severe secondary finding in adult dogs; clin-

ical signs prior to weaning; may be clinically confused with canine atopic der-

matitis (Figures 29.3, 29.4)

Keratoderma in dogue de Bordeaux: mutation in the keratin 16 gene (KRT16);

hyperkeratosis of the footpad and planum nasale

Epidermolytic ichthyosis: mutation characterized by lysis of keratinocytes asso-

ciated with hypergranulosis and hyperkeratosis corresponding with a defect

in keratin formation; Rhodesian ridgeback, nasal parakeratosis of Labrador

retriever, Norfolk terrier (epidermal keratin KRT10), cavalier King Charles

spaniel (Figure 29.5)

Cavalier King Charles spaniel: keratoconjunctivitis sicca and ichthyosiform der-

matosis; dry eye, curly coat, hyperkeratosis, footpad hyperkeratosis, nail dystro-

phy; mutation in the FAM83H gene; irregular keratin-14 labeling

Epidermolytic: lesions localized or generalized; large thick scales adhere to the

epidermis and appear scale-like; underlying epidermis thickened with accen-

tuated furrows and irregular texture (lichenification); erythema and exuda-

tion often present; fissures develop, especially with secondary infection; debris

entrapped in the hair coat resulting in severe and generalized pigmented scal-

ing; progressive alopecia may develop in severely affected areas; thick crusting

of the footpads and nasal planum; keratin fronds produce horn-like projections

(Figure 29.6)

Single case reported in an Abyssinian kitten.